Application of Organolithium and Related Reagents in Synthesis, Part X. Metallation-Electrophilic Substitution Sequence of Secondary Chlorobenzamides

Article abstract of DOI:10.1007/BF00808275

The lithiation (BuⁿLi/THF) of 2-chloro- (1), 3-chloro- (2) and 4-chlorobenzanilides (3) and the subsequent reactions of the corresponding bis-lithiated anilides 4-6 with electrophiles (MeI, CH2=CH-CH2Br, Me3SiCl, MeCHO, o-MeOC6H4CHO, p-MeOC6H4CHO, Me2NCHO and p-MeOC6H4CONMe2) towards the synthesis of the ortho substituted chlorobenzoic acids derivatives 12-14 have been described.The effect of the chlorine substituent upon the generation and stability of the bis-lithiated chloro-anilides 4-6 has been studied.It has been found that the bis-lithiated chloro-anilide 5 derived from n-chloro-benzanilide (2) at a temperature above - 30 deg C converts into the corresponding benzyne 9.The anilide moiety (masking group) of the formed ortho-substituted chlorobenzanilides appeared to be effectively removable on acid-driven hydrolysis.Keywords: Secondary chlorobenzamides; Lithiation; Electrophilic substitution; ortho-Substituted chlorobenzoic acids; Phthalides; 2,3-Dihydro-1H-iso-indolin-1-ones; 3,4-Dihydroisocoumarins.